<p>
  Pairs trading is a non-directional, market-neutral trading strategy which seeks to identify the price divergence from two highly correlated assets.
  Pairs trading assumes the co-movement and the mean reversion of two asset prices. It indicates that the price of selected assets
  tend to move together, and when they diverge, we can exploit the investment opportunity by taking a market neutral position as we assume their price will tend to move back to the average price over time.
  In this algorithm, we use a large family of international exchange-traded funds(ETFs) to examine the performance of the pairs trading strategy.
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